1. Field of the Invention
The invention is directed to an improved fuel injection system for an internal combustion engine.
2. Description of the Prior Art
One such fuel injection system, known from German Patent Disclosure DE 42 11 651 A1, has a fuel injection valve with an injection valve member, by which at least one injection opening is controlled. The injection valve member is acted upon by the pressure prevailing in a pressure chamber of the fuel injection valve and is movable by it, counter to the force of a closing spring, in an opening direction to open the at least one injection opening. Fuel is delivered under high pressure to the pressure chamber for the fuel injection. The opening pressure of the fuel injection valve, in other words the pressure in the pressure chamber, at which the pressure force acting on the injection valve member Is greater than the force of the closing spring acting on the injection valve member, and at which the injection valve member moves in the opening direction to open the at least one injection opening, is dependent only on the prestressing of the closing spring and is thus fixedly specified. To adapt the fuel injection optimally to various operating states of the engine, and to adapt the course of the fuel injection for the sake of achieving the lowest possible emissions of exhaust gas and noise, however, the opening pressure of the fuel injection valve should be variable.